Reaction of substrate compounds with fluorine in an eductor

ABSTRACT

Substrate compounds are reacted by passing them through an eductor with fluorine gas optionally in the presence of a liquid medium and preferably in a loop reactor with cooling means thereby providing rapid but controlled reaction suitable for industrial scale production. Vinylidene chloride, for example, smoothly produces dichlorodifluoroethane and dichlorotrifluoroethane in good yield.

This is a continuation of application Ser. No. 07/345,588 filed May 1,1989 now U.S. Pat. No. 5,177,275.

The present invention relates to a novel process for treating substratecompounds with fluorine. More particularly, it relates to reacting asubstrate compound with elemental fluorine in an eductor, a form of ajet pump that makes use of the momentum of one fluid to move another. Incomparison with the state-of-the art, the novel process of thisinvention is uniquely suitable for rapid treatment of substratecompounds with fluorine in a controlled manner, allowing large-scaleproduction of valuable products.

BACKGROUND OF THE INVENTION

Prior art has previously demonstrated that reaction of substratecompounds using elemental fluorine is a highly exothermic process,making it difficult to obtain good yields of the desired products of thereaction and scale-up to industrial production. Attempts to control thereaction have involved the use of the dilute fluorine (1-20%) in aninert diluent (N₂, Be, Ar) at low temperature (-70° C. to -85° C.) anduse of an inert solvent (CFCl₃, CF₂ Cl₂, CFCl₂ CF₂ Cl) [Eur. Pat. Appl.No. 0 219 823 A1 dated Apr. 29, 1987; S. Rozen and C. Gal, J. Org. Chem,(1987) , 52 2769]. Even with the use of such mild conditions, in orderto control the exotherm and prevent unwanted side reactions, the rate offluorine addition is less than 80 ml min⁻¹ (less than 7.6 g hr⁻¹), thusmaking large scale reactions impractical. Other techniques, such as the"LaMar" method [for example R. J. Lagow et al, J. Org. Chem, (1989), 541990] or Aersol Direct Fluorination [J. L. Adcock et al, J. Am. ChemSoc., (1981) , 103 6937] both involve sophisticated apparatus and low F₂flow rates (less than 60 ml min⁻¹) , again unsuitable for large-scaleproduction. It has now been discovered that by the use of an eductor forthe introduction of fluorine, preferably in a loop reactor havingcooling zones, e.g., cooling coils equipped to be externally cooled,substrate compounds can be treated with fluorine rapidly in a controlledmanner with fluorine rates as high as possible based on desired reactioncontrol, thus making large-scale fluorine reaction a viable process.Substrate compounds that can be treated with fluorine by this processinclude, but are not limited to alkenes, cycloalkenes, alkynes, allenes,aliphatics, cycloaliphatics, aromatics, compounds with multiple bonds(>C═N--, --C.tbd.N, >═O, etc.,) compounds of sulfur, nitrogen,phosphorus, iodine, bromine, chlorine, oxygen, silicon, and the like.Such compounds can be organic or inorganic. The term "fluorination" isused herein in its broadest sense: fluorine can react by addition,substitution, oxidation, polymerization and any other reaction wherefluorine may, or may not, be present in the final product. Thus there isused the term "substrate compound" to contemplate as a starting materialany compound having fluorine-reactive sites.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings are intended to facilitate understanding the invention.

FIG. 1 represents in flow diagram form an apparatus suitable forreacting a substrate compound with fluorine by means of a loop reactorutilizing an eductor and cooling coils in accordance with the presentinvention.

FIG. 2 is an elevated cross section showing in greater detail one typeof eductor suitable for use in the apparatus shown in FIG. 1.

FIG. 3 is an elevated cross-section of another type of eductor suitablefor use in the apparatus shown in FIG. 1.

SUMMARY OF THE INVENTION

According to the present invention there is provided a processcomprising

(a) reacting

(i) a substrate compound or a mixture of such compounds having at leastone site for fluorination with

(ii) elemental fluorine, alone, or in admixture with an inert gas, in aneductor until the reaction is substantially complete; and

(b) recovering,

(i) a reacted substrate compound,

(ii) a mixture of such compounds or

(iii) an oligomeric derivative of (i) or (ii).

Preferably, the process is carried out in a loop reactor comprisingcooling zones for controlling the heat of reaction with fluorine. In apreferred embodiment, the reaction temperature is from about -80° C. toabout +100° C. The process can be carried out with a reaction mixtureconsisting essentially of (a)(i) and (a)(ii); alternatively, the processcan be carried out with a reaction mixture comprising (a)(i), (a)(ii)and (a)(iii), a liquid medium, at a temperature of about the mediumfreezing point to about the medium boiling point. If a medium is used,preferably it comprises a perhalogenated organic liquid or an inorganicliquid selected from water, hydrogen fluoride, and the like, or amixture of any of the foregoing. The invention contemplates in apreferred embodiment processes in which the substrate compound (a)(i) iscapable of reacting with fluorine by (1) adding fluorine across amultiple bond; (2) replacing hydrogen by fluorine; (3) replacing halogenby fluorine; or a combination of any of (1), (2) and (3), particularlywhen (a)(i) comprises a halohydrocarbon or a mixture thereof.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, the novel process using elemental fluorine of thisinvention conveniently utilizes a loop reactor 2 through which is pumpedfrom flask 4 the reaction mixture containing the substrate compound tobe treated with fluorine optionally suspended or dissolved in a liquidmedium (CFCl₃, CF₂ Cl₂, CCl₄, etc) at high flows, e.g., greater than 8 1min⁻¹. Fluorine is introduced to the reaction mixture via the eductor 8either undiluted (100%) , or diluted with nitrogen or other inert gas asdesired or as required, the total flow of gas is generally many timesthat which can be added without the use of this technique. The presenceof eductor 8 leads to highly efficient mixing between the reactionmixture and elemental fluorine. Any resulting highly exothermic reactionis controlled, however, by passage of the circulating reaction mixturerapidly through externally cooled coils 10 and 12. Doing so will providehighly efficient cooling at the point of fluorine addition, therebypreventing hot spots and undesired side-reactions. For example, 100%fluorine can be added to selected substrate compounds, e.g., unsaturatedorganics, at -70° C. at the rate of 1200 ml min⁻¹ to produce the1,2-addition product with negligible (less than 10% by-productformation). This represents a rate of fluorine addition twenty-fivetimes greater than has been previously attainable and the use ofmultiple eductor/cooling coils (not shown) in the reactor loop wouldfurther greatly enhance capacity.

The system of fluorine treatment of this invention is not restricted toelectrophilic fluorinations (temperature generally less than -40° C.),but it will also find application in controlled radical reactions(temperature generally more than -40° C.), because the rapid mixing andhighly efficient heat transfer enable the exotherm to be easilycontrolled by the temperature of the circulating reaction mixture.

The eductor used in the present invention can vary broadly in structureand materials of construction without ceasing to function in the desiredmanner. Where corrosion is excessive, fluorine- and HF-resistantmaterials of construction will, of course, be selected for the eductoras well as other system components. Suitable, for example, are stainlesssteel, carbon steel, nickel, Monel®, Hastelloy C®, copper, brass,Teflon®, and many others Alternative designs are well known to thoseskilled in this art and many are available commercially. Reference ismade to Perry and Chilton, Chemical Engineers Handbook, 5th Edition,McGraw-Hill, 1973, 6-15.

In general, any jet pump of the ejector type can be used. Preferably,however, the pumping fluid as is shown in FIGS. 2 and 3 will enterthrough a nozzle and thereafter pass through a venturi nozzle 16 thenout through a discharge opening 18. As the fluid passes into the venturinozzle, it develops a suction that causes the fluorine or mixture offluorine and any inert gas, e.g., nitrogen, in the suction chamber 20 tobe entrained with the stream and be delivered through the discharge 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The following examples illustrate the invention but are not intended tolimit the claims in any manner whatsoever.

EXAMPLE 1

A solution of vinylidene chloride (500 g) in CFCl₃ (15.1) was circulatedthrough the eductor and loop as generally shown in FIG. 1 at -70° C.(all baths cooled with CO₂ /acetone.sub.). Fluorine was introduced tothe circulating liquid medium via the eductor, initially at aconcentration of about 10% (91 ml min¹) in nitrogen (755 ml min⁻¹) for30 mins, the temperature rise was controlled to -68° C., i.e., a 2° C.exotherm. During the next 60 mins., the fluorine flow was graduallyincreased and the nitrogen flow decreased until after 100 mins., 100%fluorine was being added at the rate of 1200 ml min⁻¹ ; the temperatureread -63° C. at this point. Fluorination was continued for a further 90mins. under these conditions, at which stage analysis of the reactionmixture by gas chromatography (GC) showed in addition to CFCl₃, CF₂HCFCl₂ and CFH_(2k) CFCl₂ in a ratio of 1:3.22 with less than 10%unwanted by-products. Thus approximately 90% of the product mixture isattributable to the desired electrophilic fluorination with only a smallamount of oligomeric by-products, even though 100% fluorine was used.

EXAMPLE 2

A solution of vinylidene chloride (2500 g) in CFCl₃ was circulatedthrough the eductor loop shown generally in FIG. 1 at -71° C. Fluorinewas introduced rapidly at the rate of 1200-1600 ml min⁻¹ such that thetemperature at the eductor was 50°-100° C., but rapidly quenched to lessthan -60° C. by the cooling coils. Fluorination was continued underthese conditions for 5 hours until approximately 50% of the vinylidenechloride had been consumed. Gas Chromatographic (GC) analysis of thereaction mixture showed no CFH₂ CFCl₂, the product expected by additionof fluorine across the double bond; but instead, a product correspondingto a dimer, the identity of which is not clearly understood at thistime, was formed in 70% yield (as calculated by GC and based onunreacted starting material). The detection of chlorine in the off-gasesof the reaction was considered evidence of a free radical process.

The above-mentioned publications and patent and/or applications areincorporated herein by reference.

Many variations of the invention will suggest themselves to thoseskilled in the art in light of the foregoing detailed description. Forexample, instead of vinylidene chloride, vinyl chloride, benzene, carbondisulfide, diphenylacetylene, ethane, acetonitrile, carbon monoxide, andmany others, as well as mixtures of any of them, can be used as startingmaterials. The reaction can be carried out in the absence oftrichlorofluoromethane, or with water and/or hydrogen fluoride as liquidmedia. Instead of a mixture of fluorine and nitrogen, fluorine alone canbe fed to the eductor or fluorine mixed with argon and the like can befed. The cooling coils can be omitted. All such obvious variations arewithin the full intended scope of the appended claims.

We claim:
 1. A process comprising(a) inducing movement in a fluid streamwhich is or contains a substrate compound having at least onefluorine-reactive site to provide a moving substrate stream (b) eductingelemental fluorine, alone, or in admixture with an inert gas, into thestream of fluid substrate whereby said fluorine is reacted rapidly withsaid substrate in a controlled manner; and (c) recovering a reactedsubstrate compound, a mixture of such compounds or an oligomericderivative of such compound or compounds, andwherein step (b) is carriedout in an eductor comprising a venturi nozzle having a throat fordirecting the moving fluid substrate and a suction chamber forintroducing fluorine upstream of said throat into said moving fluidsubstrate.
 2. A process as defined in claim 1 carried out in a loopreactor comprising cooling zones for controlling the heat of fluorinereaction.
 3. A process as defined in claim 1 wherein the reactiontemperature is from about -80° C. to about +100° C.
 4. A process asdefined in claim 2 wherein the reaction temperature is from about -80°C. to about +100° C.
 5. A process as defined in claim 1 carried out witha reaction mixture consisting essentially of said substrate compound andelemental fluorine.
 6. A process as defined in claim 1 carried out witha liquid stream comprising said substrate compound, elemental fluorine,alone, or in admixture with an inert gas and a liquid medium, at atemperature of from about the medium freezing point to about the mediumboiling point.
 7. A process as defined in claim 6 wherein the liquidstream includes a perhalogenated organic liquid or an inorganic liquidselected from water, hydrogen fluoride or a mixture of any of theforegoing.
 8. A process as defined in claim 1 wherein said substratecompound is capable of reacting with fluorine by(1) adding fluorineacross a multiple bond; (2) replacing hydrogen by fluorine; (3)replacing halogen by fluorine; or a combination of any of (1), (2) and(3).
 9. A process as defined in claim 8 wherein said substrate compoundcomprises a hydrocarbon, a halohydrocarbon or a mixture thereof.
 10. Aprocess as defined in claim 1 further comprising the step of deliveringthe fluorine to a venturi at a location upstream of the convergentsection of the venturi.
 11. A process as defined in claim 10 wherein thefluorine is delivered to the venturi normal to the axis of the venturi.